You may just be having generalized multimedia problems. This is the downside of free, as in speech, Linux distributions. You more often than not have to do extra work to get the the multimedia to function. It's purely a legal thing that makes Linux look less than it is.
This is one of the things I really like about Mint. They've automated the process to the point it's almost invisible.
Have you done this:
http://ubuntuguide.net/how-to-install-mplayer-and-multimedia-codecs-in-ubuntu-910karmicI don't love the way these instructions are laid out, but I can get the site that normally has a good set of these to load at the moment. However, they work.
Do that if you haven't. It'll make a lot of your multimedia problems go away.
As for a DVD burner, I use k3b, which is a KDE app and isn't in the default repositories. Everything for burning is based on using the same command line utilities. All you're choosing is a GUI, some of which are better than others. I'm accustomed to k3b, so that's what I stick with.
Gnome Baker is supposed to be nearly as good and is integrated into the distro you're using.
sudo apt-get install gnomebaker
You also might look through this. Note that you'll have to make sure your sources list is is the same as his so that it's checking all the right places when you install packages. He provides it for you. Just replace your own /etc/apt/sources.list with his karmic.sources.list. (You'll have to rename his list to sources.list of course.) I'd back up your old one first.
Edit: My dumb ass forgot the URL
http://tnoergaard.wordpress.com/2009/11/01/to-do-list-after-installing-ubuntu-9-10-aka-karmic-koala/From whatever directory you download it to (the first line is making a backup of your old sources list; reverse that if something goes wrong):
sudo cp /etc/apt/sources.list sources.list.mine
sudo mv karmic.sources.list /etc/apt/sources.list
Then you gotta do the keys thing he mentions to keep apt-get and synaptic from crying at you.
sudo apt-get update
Then do whatever he says to do to install whatever you want. k3b is listed.
Again, you can do all this with Synaptic and a GUI, but I don't use it and can't do instructions on it well. It's straightforward, but the CLI method is actually faster.